Mathematical appendix

Abstract

Messages from a source, seen as symbols xj from some alphabet, each having probabilities Pj associated with a random variable X, are ‘encoded’ into the language of a ‘transmission channel’, a random variable Y with symbols yk, having probabilities Pk, possibly with error. Someone receiving the symbol yk then retranslates it (without error) into some xk, which may or may not be the same as the xj that was sent.